In race one Evans hooked up well when the lights went out and led the field into turn one from Briton Alex Lynn. The race was red flagged after Bruno Bonifacio mounted the rear of Jann Mardenborough's car to end up high in the air.
At the restart Evans and Lynn were at it hammer and tongs again but the Briton couldn't get past as there was too much debris off the racing line.
"We had a great battle out there but there weren't many places I could safely have a go at overtaking. Mostly I just stayed in Mitch's mirrors and looked for a mistake," said Lynn.
Pipo Derani came home third with Cassidy fourth and Auer fifth, meaning Cassidy extended his lead in the championship to 11 points.
Taking advantage of the reverse top four finishers grid for race two, Cassidy took off like Lance Armstrong on steroids to take his first win of the series and further extend his lead over Auer in the championship.
Derani backed up his race-one result with another podium finish with Auer rounding out the top three, and Lynn came home fifth to settle into third place in the race for the title.
"It was good to get that little monkey [first race win] off my back but even better to get a bit more of a points buffer in the championship over Lucas in the series," said Cassidy.
The series is nicely poised for a major showdown in Manfeild next weekend with any one of five drivers in with a chance.
